Boat lifts are used to raise boats and other personal watercraft out of water and lower boats and other personal watercraft into the water. Boat lift systems can use a variety of means to power the lifting function including electric motors, hydraulic and pneumatic systems and manual cranks. Boat lift systems using electric motors are often powered by electric power across the line. In such a system, the motors operate at a fixed voltage and frequency. This results in the motors operating at a fixed speed and torque. Boat lift motor systems lacking in the ability to vary the speed and torque of the motors are also lacking with regard to position control in that the boat lift may not be able to provide beneficial motor control, such as, for example, independently variable lifting speeds for a range of boats and other watercraft. This provides disadvantages as to flexibility in using the boat lift for boats and other watercraft of varying size.
For boat lifts that employ multiple motors, synchronization of the motors can pose difficulties, for example, due to the sensitivity of the motors to slight fluctuation in the electric power. Because each individual motor is usually attached to a separate part of the boat lift cradle device, the lack of synchronization in the motors can result in an uneven raising or lowering of a boat. If the speed between the motors is too great, the boat lift cradle will become too far out of level to continue to move safely, thus necessitating correction.
Existing methods of leveling a boat lift are to manually stop the motors and for the user to manually run one motor at a time to adjust the boat lift cradle to return to a level position. These systems lack the ability automatically level the boat lift without stopping the motors and thus add a significant amount to time in raising or lowering the boat lift. Such starting and stopping can furthermore reduce the life of a motor.